MegaRAID SAS Driver get unexpected Interrupt.  Add the dummy readl to
force PCI flush will fix this issue.
Signed-off-by: NBo Yang <bo.yang@lsi.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Cc: Stable Tree <stable@kernel.org>
Signed-off-by: NJames Bottomley <James.Bottomley@HansenPartnership.com>